The present invention relates to an air bag system for protecting a vehicular occupant against the impact of a collision by feeding gases to inflate an air bag, when the collision is detected, so that the air bag may be expanded between the occupant and a structural component of the vehicle compartment to establish an impact buffing zone. More particularly, the present invention relates to an operation control system for the vehicular air bag system, which includes means for preventing the air bag from being expanded, if unnecessary as at the time of a non-collision.
In a vehicle equipped with an air bag system for a vehicular side collision, there is a technology of arranging the side door with a touch sensor for detecting a side collision of the vehicle. The side door of the vehicle equipped with the side collision air bag system is disclosed in Japanese Patent Laid-Open No. 281459/1991, for example. In order to detect a side collision quickly, as shown in FIG. 22, a collision sensor 3 is attached to the outer side (as located at the lefthand side of FIG. 22) of a side impact beam 2 arranged generally horizontally in a side door 1 and is positioned close to the inner face of the outer panel 4 of the side door 1.
This collision sensor 3 has its contacts connected, if it is clamped between the outer panel 4 to be deformed inward at the time of a side collision of the vehicle and the side impact beam 2. If the collision sensor 3 thus detects the side collision, an inflator 5 is fed with an igniting current so that it is ignited. The ignited inflator 5 produces inert gases to inflate an air bag 7 which is confined in a folded state in an arm rest 6, for example, so that the air bag 7 is expanded between the inner face of the side door 1 in the compartment and the occupant thereby to protect the occupant from a secondary collision.
In the side collision air bag system, as described above, the collision sensor 3 is often arranged close to the inner face of the outer panel 4 in the side door 1 so as to detect the side collision quickly. Thus, the outer panel 4 may be deformed to turn ON the collision sensor 3 at the time other than the side collision if a considerable force is applied to the outer side of the side door 1.
Especially the collision sensor of touch switch type is held to have closed contacts, once it is compressed to have its contacts closed as a result of a plastic deformation of the outer panel 4. Let the case be considered, in which an external force is applied to the side door 1 of a vehicle being parked with no passenger so that the outer panel 4 is plastically deformed to close the contacts of the collision sensor 3. At this instant, the air bag is left unexpanded because the ignition switch (i.e., the main switch of the vehicle) is OFF. When the driver turns ON the ignition switch for starting the vehicle, there arises a disadvantage that the inflator igniting circuit is made to expand the air bag because the contacts of the collision sensor 3 are closed.